642440 has 16 divisors (see below), whose sum is σ = 1445580. Its totient is φ = 256960.

The previous prime is 642427. The next prime is 642457. The reversal of 642440 is 44246.

It can be written as a sum of positive squares in 2 ways, for example, as 538756 + 103684 = 734^2 + 322^2 .

It is a Harshad number since it is a multiple of its sum of digits (20).

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 642440.

It is an unprimeable number.

642440 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7991 + ... + 8070.

2⁶⁴²⁴⁴⁰ is an apocalyptic number.

It is an amenable number.

642440 is an abundant number, since it is smaller than the sum of its proper divisors (803140).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

642440 is a wasteful number, since it uses less digits than its factorization.

642440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16072 (or 16068 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 20.

The square root of 642440 is about 801.5235492486. The cubic root of 642440 is about 86.2867658141.

Adding to 642440 its reverse (44246), we get a palindrome (686686).

The spelling of 642440 in words is "six hundred forty-two thousand, four hundred forty".